Build a Basement Root Cellar

Storing crops in a passively cooled basement root cellar is one of the most efficient ways to preserve food.

By Steve Maxwell

| December 2004/January 2005

The two vents create a siphon effect that lets you regulate the flow of cold outside air into the insulated cellar room, allowing the temperature to remain near freezing through the winter months. As you custom-cut your wall studs to length, make them short enough to leave an eighth- to a quarter-inch gap between the top of the wall and the joists above when combined with the top and bottom plates. Basement floors are often damp, so consider using composite deck material instead of wood for the bottom wall plate. Insulation is your next challenge, and good reasons exist to consider using rigid sheets of foam instead of traditional fiberglass batts. The most important is moisture resistance.Illustration courtesy Len Churchhill

Traditionally, this cold room was an underground space built under or near the home, insulated by the ground and vented so cold air could flow in and warm air out in the fall. Then when winter temperatures arrived, the vents were closed, and the cellar stayed cold but not freezing.Photo courtesy Len Churchhill

The great thing about cabbage, carrots and all the other crops, as David Cavagnaro and Nancy Bubel describe in the two previous articles, is all you need to store them for months is a cold, well-ventilated space. A spare refrigerator works pretty well, but even better and more spacious is a real root cellar. A basement root cellar is convenient and useful.

Traditionally, this cold room was an underground space built under or near the home, insulated by the ground and vented so cold air could flow in and warm air out in the fall. Then when winter temperatures arrived, the vents were closed, and the cellar stayed cold but not freezing.

Most modern basements are too warm for long-term winter storage, but you can create an indoor version of the cellars that have long served homesteaders well by walling off a basement corner and adding the vents, as shown in the drawing above. The two vents create a siphon effect that lets you regulate the flow of cold outside air into the insulated cellar room, allowing the temperature to remain near freezing through the winter months.

Fred Matlack of Vera Cruz, Pa., developed this nifty design, and the basement root cellar he built in his basement has worked just as he planned. “You just need to watch the temperature to be sure you close the vents before the temperature drops below freezing, which would damage some crops,” Matlack says.

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Several universal truths remain constant that will help you create an optimal root cellar, even though every basement situation is unique. The first is location. Because you’ll need access to the outdoors for fresh air, choose a cellar position that includes a window. It’s possible to bore holes through a basement wall for the 3- or 4-inch vent pipes you’ll need to install, but it’s a whole lot easier to simply remove the glass from a window, replace it with plywood and then run your pipes through holes in the wood. In cold regions, you can create an insulated panel to replace window glass. Laminating a layer of half-inch-thick exterior-grade plywood on each side of a piece of 1- or 2-inch-thick extruded polystyrene foam is a terrific way to make an insulated panel for vent pipe access. Polyurethane construction adhesive is perfect for holding the foam-and-wood sandwich together.

When it comes to any basement root cellar, the exterior walls create ideal interior temperatures. This is what delivers the cooling action, and the more masonry surface you’ve got, the better. That’s why you’ll want to choose a corner location for your installation if you can. This offers maximum exposure to exterior walls while minimizing the need to build and insulate interior walls. And if you’ve got a choice, select a spot with the highest soil height outside. Does one of your possible options include northern exposure? Terrific! That’s great if you can get it.

After you’ve picked your cellar location and replaced the window glass with a solid panel that accommodates the vent pipes, turn your attention to the walls. Find yourself a helper, grab a sheet or two of plywood or wafer board, and get ready to use your imagination. It’s amazing how temporarily propping up sheet materials can help you imagine the floor plan of a new room, leading you to better finished results. How long should your cellar be? How wide? Is a 3-foot-wide door big enough? These kinds of questions are much easier to answer when you’ve got something to hold up, look at, move around and tweak.

With the footprint and door location of your cellar finalized, mark the relevant outlines on the floor with a big felt-tipped marker. Although you’ll need to build some kind of wood frame for the wall and doorway, it needn’t be as beefy as a typical load-bearing wall for a house. You can extend stud spacing beyond 24 inches on center if you need to economize, but regardless of the wall design, you’ll have to secure it at the top and bottom. A few tricks can make this happen.

As you custom-cut your wall studs to length, make them short enough to leave an eighth- to a quarter-inch gap between the top of the wall and the joists above when combined with the top and bottom plates. That way, you’ll have no trouble tilting the wall up into position (be sure to check that it’s plumb by using a level), yet you still can secure it with 3½-inch #10 screws driven up through the top plate and into the bottom edge of the joists. Drive a softwood wedge dabbed with glue into the gap before driving the screws home.

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Basement floors are often damp, so consider using composite deck material instead of wood for the bottom wall plate. Choose a brand that’s solid all the way through, then cut and nail it just like regular lumber. Composites are rot-proof and won’t contribute musty smells to your cellar, even if they get wet. Anchor the bottom of your cellar wall to a concrete floor with construction adhesive and concrete nails or screws driven into pre-drilled holes.

Insulation is your next challenge, and good reasons exist to consider using rigid sheets of foam instead of traditional fiberglass batts. The most important is moisture resistance. Any basement is likely to get damp from time to time, and fiberglass has almost no ability to resist mold growth and deterioration when water is present. Foam, on the other hand, tolerates moisture much better. It’s also easier to use than fiberglass, and it’s non-irritating. Extruded polystyrene is especially good in this regard. It’s also a highly effective thermal insulator. Just be aware that some jurisdictions require foam to be covered with a fire-resistant sheet to meet code specifications. As you plan your insulation strategy, be sure to include the ceiling of your cellar. Warmth coming down from heated areas above could raise cellar temperatures too high for the food.

A key feature of the basement cellar is the two-vent design. To function optimally, space the interior ends of the intake and exhaust pipes as far apart as possible. Also, you’ll need to plan your shelf layout to allow as much top-to-bottom air movement as you can achieve. This is where ceiling-mounted shelves can really help. The best idea is to use hanging metal wire frames that support shelves made of 2-by-12-inch lumber you cut yourself. Cover the vent openings with screen to keep out insects and mice, and if you want to really cool the room down quickly, add a little exhaust fan to supplement the natural flow of cool air down into the room.

Contributing Editor Steve Maxwellhas been helping people renovate, build and maintain their homes for more than two decades. “Canada’s Handiest Man” is an award-winning home improvement authority and woodworking expert. Contact him by visiting his website and the blog, Maxwell’s House. You also can follow him on Twitter, like him on Facebookand find him on Google+.

Share your thoughts.

www.EasyWoodwork.org

5/7/2018 2:06:50 AM

I used the plans at WWW.EASYWOODWORK.ORG to build my own cellar – I highly recommend you visit that website and check their plans out too. They are detailed and super easy to read and understand unlike several others I found online. The amount of plans there is mind-boggling… there’s like 16,000 plans or something like that for tons of different projects. Definitely enough to keep me busy with projects for many more years to come haha Go to WWW.EASYWOODWORK.ORG if you want some additional plans :)

jamespond

10/30/2013 4:38:30 PM

I've posted twice now, and don't see the two postings anywhere.

jamespond

10/30/2013 3:13:35 PM

to MAC.... the best you can do is secure a few OLD,USED refrigerators (4 or 5), build a 'room simialr to the 'celler 'root celler'' depicted in this email, in you garage. Make the walls top and bottom, very well sealed and insulated. Remove the doors from the 'non working' refrigerators AND the one that works. Have that working one set on a thermostat timer, set at 45F to 50F
so when the temp reaches the lower setting, the working frig turs off, then on when the temp exceeds 50. I would insulate the concrete floor as well, with a solid foam sheet, with 1/2 plywood on top so you can walk without crushing the foam. Seal all the edges with a white tub sealer. include a fan for minimal air flow to prevent excess moisture development...at the top of the wall so as to keep the cold dense air in... good luck.

We built this root cellar in our basement two years ago in the north corner of our basement. Below grade concrete on two walls, concrete covered with linoleum tile on the floor, and two sides and a ceiling of well-insulated wood. I built red oak bins around the base, filled them with sand, and buried turnips, beets, and potatoes. In the winter, the humidity never gets higher than 45%. We've sprayed the sand with water, drenched towels and hung them over the bins, to no avail. The sand is dry as a bone and nothing keeps well. I believe the flaw in the design is there is no insistence on a dirt wall or floor. We're building another root cellar outside this summer.

Akira

4/21/2011 11:46:18 PM

so question, my basement is half below and half above ground. can i do this that way or do i have to build the basement too?

Glenndora_2

10/12/2010 10:56:05 PM

For humidity, just keep a household type of spray bottle down there with water, and each time you go get some veggies, spray the floor a little bit. Also, it seems like simply leaving the basement window is simple, if it is one of those crank-out types, then make sure you have screening of some sort, and simply open the window more or less as needed. Hanging a wall thermometer away from the direct window draft helps too. Happy eating!

Chris_69

5/5/2010 3:18:37 PM

With carrots and parsnips, and possibly others, supposedly the best thing is to leave them in the ground covered with a thick layer of mulch. I haven't tried this but from what I've read the flavor improves and they can be dug up as needed as the mulched ground doesn't freeze hard; also they're really good in early spring. I do know that kale tastes incredibly good after a hard freeze. One of these years I will manage to try these methods...

Brandis

5/5/2010 10:48:09 AM

Do you keep your root vegetables (other than potatoes) in wet sand? That's what I've always heard to do, and I would imagine that would keep vegetables from becoming dehydrated.

Gordon Henry

5/5/2010 10:20:00 AM

I understand the need to bring in cold air but. I have a concern about the humidity getting too low, because of the cold dry air coming in and ending up with dehydrated veggies.
I have an insulated / unheated (except for what may radiate down through the main floor) crawlspace. In the coldest part of winter this space only gets down to about 48f. my carrots only last 1-1 1/2 months before becoming uneatable carrot jerky :( I have been able to extend that some by keeping them in a partly covered container, but there is a fine line with that too. Not enough air and they get moldy.
I know I need to get them colder. But what about the humidity? If I put a humidifier in there, what level should I try to maintain?
Gordy

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